2011 Annual Report
1a.Objectives (from AD-416)
Objective 1. Develop integrated and commercially feasible pre-harvest practices and treatments to maintain quality and extend the shelf and shipping life of fresh fruit (primarily citrus fruit and table grapes).
Objective 2. Develop integrated and commercially feasible postharvest practices and treatments to maintain quality and extend the shelf and shipping life of fresh fruit (primarily citrus fruit and table grapes).
1b.Approach (from AD-416)
A variety of preharvest and postharvest actions and chemical treatments to extend the shelf life and maintain quality of fresh citrus fruit and table grapes will be developed and evaluated under laboratory and semi-commercial conditions. Promising treatments will be combined in integrated regimes later in this project. Replacing 5302-43000-035-00D (9/2010).
This report documents progress for the parent Project 5302-43000-036-00D “Maintaining Quality and Extending Shelf And Shipping Life Of Fresh Fruit with No or Minimal Synthetic Pesticide Inputs” which started October 2010 and continues research from Project 5302-43000-035-00D “Emerging Technologies to Maintain Postharvest Quality and Control Decay of Fresh Commodities.” Mandarins are often held at warm temperatures prior to sale, yet it was previously shown that this type of storage causes a rapid loss of flavor quality in the variety ‘W. Murcott’. Six additional varieties were screened for this response in 2010-2011 and all but one responded in the same manner as ‘W. Murcott’. Timing of the response was determined by performing periodic taste tests during storage. The loss in flavor quality was associated with changes in flavor volatiles that are accentuated by warm temperatures. Postharvest decay annually causes significant losses of fresh citrus fruit and table grapes. Effective control of postharvest citrus diseases by fungicides has declined because of the proliferation of fungicide resistance isolates of the decay pathogen Penicillium digitatum. In recent and previous work, brief postharvest treatments with heated potassium or calcium phosphite effectively controlled decay of citrus alone, improved the performance of several common fungicides when they were used together, and partially controlled fungicide-resistant isolates of the pathogen. Its pre-harvest use was not promising for this pathogen, but good for the control of another disease, brown rot caused by Phytopthora spp. Tests in packinghouses were conducted in 2010 to facilitate phosphite registration and its commercial adoption. Supplemental potassium fertilization, applied directly into grape clusters, markedly improved the firmness, color, and sugar content of many additional cultivars in 2011, increased chitinase activity, and caused some reduction in postharvest decay, mostly caused by Botrytis cinerea. After harvest, storage in a low concentration of ozone gas prolonged the storage life of table grapes under commercial conditions by an additional 2 to 3 weeks. In 2011, tests within commercial storages were conducted to evaluate grape packaging, and some can inhibit ozone diffusion and render it less effective.
Effect of storage on the flavor of mandarin oranges. Mandarin oranges are popular with consumers but often develop poor flavor during storage. Taste tests that were conducted on fruit stored using several combinations of both warm and cold temperature storage indicated that storage at warm temperatures, even for a short period of time, can negatively alter flavor, especially if the fruit has previously been in cold storage. ARS researchers at the San Joaquin Valley Agricultural Sciences Center identified changes in flavor components in the fruit were found to be a likely cause of this loss in flavor quality. This information can be used to develop new storage protocols for mandarin oranges to preserve flavor after harvest and maintain consumer acceptance.
Obenland, D.M., Margosan, D.A., Smilanick, J.L., Mackey, B.E. 2010. Ultraviolet fluorescence to identify navel oranges with poor peel quality and decay. HortTechnology. 20:991-995.